The present invention relates to optical display systems. More specifically, the present invention relates to an optical display system with improved light projection efficiency.
A typical projection system includes an arc-lamp source of bright white light, a method for separating the white light into red, green and blue spectral components, and a spatial light modulator (SLM, also called a light valve) for two dimensional imaging each of the spectral components to create a color picture. The SLM performs the spatial and temporal modulation in response to an analog or digital video signal generated by a computer or another video source such as a TV tuner, VCR, HDTV broadcast, or DVD player. The SLM creates sequential images typically in red, green and blue color planes although other color separation techniques exist such as cyan, yellow, magenta and optionally white planes. The color planes may then be recombined optically and projected onto a screen, or they may be flashed temporally in sequence onto the screen at such a rate that a viewer perceives only a single image.
There are several problems with existing arc-lamp sources. The most commonly used lamp source is a mercury vapor arc lamp. This lamp produces the most light for a given wattage and has a small point source. However, it has a short lifetime compared to other technologies and produces light that is spectrally deficient in the red spectrum. In addition, mercury is a hazardous material that many countries would like limit the use of or ban outright. Although other bulb technologies could be substituted for the mercury vapor arc lamp, none have its efficiency and small spot size that allow for production of small high intensity projectors. Therefore, there is a need for a solution that allows other bulb technologies to compete with mercury vapor arc lamps.
Most digital projectors compete on the basis of the number of screen lumens that the projector places on the projection screen. Although the competition in the projector market is fierce, cost considerations as well as size constraints have limited the development of more efficient optical designs for other light sources.
There exists a need to overcome the problems associated with arc lamp bulbs, particularly mercury vapor types. Simply replacing the arc lamp bulb with a non-arc lamp will not offer a satisfactory competitive solution because of the non-point source nature of non-arc lamps.